In our continuing effort to improve the standardization program of allergenic extracts, our laboratory is actively pursuing the project in the identification and molecular characterization of major allergens. Our studies include:Latex allergens: Methods: Twenty-six sera were obtained from adult latex allergic patients, both hospital worker and non-hospital workers. Two serum pools were obtained from children with spina bifida and adult latex allergic patients. Proteins from C-serum and latex particles of latex sap (non-ammoniated) were separated by different gel electrophoretic techniques and evaluated for specific IgE binding by immunoblotting.Results: Fifty percent of the sera tested reacted to an 18 kd protein and an acidic protein, pI 3.5, MW 25.6 kd, while only 23% of the individual allergic sera tested reacted to the rubber elongation factor (REF) which has been reported to be a major latex allergen. The immunoreactive patterns of children's and adults' serum pools are similar but not identical.Conclusions: Using different electrophoretic and transferring/blotting techniques, different immuno-reactive proteins were identified in C-serum and latex particles of latex. REF, which reacted to only 23% of sera tested, does not appear to cross react immunologically with other latex allergens.Apple allergens: We have screened 34 allergic sera which are reactive to tree pollens and apple fruit extracts. The major allergens in apples are proteins with MW of 38 kd, 31 kd, 18-17 kd, and 13-14 kd. The N-terminal amino acid sequences of 18 kd and 31 kd allergens were determined. Both proteins bear some degree of sequence homology to pathogenesis-related response proteins. We also find that store purchased apple has relatively higher allergens than freshly picked apple. The amount of 18 kd protein increases after storage. The increase of the 18 kd protein seems not due to the maturation but to infection. We also compare those allergens among different varieties of apples. It shows that golden delicious and granny smith have higher level of 18 kd allergen.